1. Field of the Invention
The present invention relates to a direct fuel injection internal combustion engine in which a fuel is directly injected into a combustion chamber. More particularly, the present invention relates to a direct fuel injection internal combustion engine in which a fuel injector is installed in a cylinder head above a center portion of a piston and positioned higher than a combustion chamber top surface formed by the cylinder head.
2. Background Information
In a conventional direct fuel injection internal combustion engine, a fuel injector is arranged so that a tip of the fuel injector faces in a combustion chamber. Such conventional direct fuel injection internal combustion engine is configured and arranged to perform stratified combustion by injecting fuel from the fuel injector during a compression stroke to form a stratified fuel-air mixture in a prescribed operating region. In such conventional direct fuel injection internal combustion engine, the fuel consumption of the engine in low load regions and medium load regions can be greatly reduced by stratifying the fuel-air mixture when the engine is operating in these regions.
Japanese Laid-Open Patent Publication No. 11-082028 (paragraphs 0010 to 0012) discloses such a conventional direct fuel injection internal combustion engine in which a fuel injector is arranged above a center portion of a piston and in which a spark plug is arranged closely adjacent to the fuel injector. The direct fuel injection internal combustion engine described in this publication has a layout interference problem between the fuel injector and the spark plug. More specifically, if the fuel injector is installed in a fuel injector opening formed in the cylinder head along the center axis of the cylinder, the spark plug has to be installed in the cylinder head either between an intake port and the fuel injector opening or between an exhaust port and the fuel injector opening. In either case, the space available for installing the spark plug is limited to avoid interference with the intake or exhaust port. Particularly, if the spark plug is installed between the exhaust port and the fuel injector opening, it is necessary to install the spark plug sufficiently far from the exhaust port in order to protect the spark plug from heat of the exhaust gas. Thus, in such case, the degree of design freedom with respect to the layout of the spark plug is further limited.
In order to solve such layout interference problem, Japanese Laid-Open Patent Publication No. 6-042352 (FIG. 1) discloses a direct fuel injection internal combustion engine in which a position of the fuel injector is shifted upward relative to a bottom surface of a cylinder head that forms an upper surface of a combustion chamber (hereinafter referred as “a combustion chamber upper surface of the cylinder head”). More specifically, in the direct fuel injection internal combustion engine disclosed in this publication, a recessed part is provided in the cylinder head that communicates with the fuel injector opening and the combustion chamber such that a tip end of a nozzle of the fuel injector is positioned within the recessed part. The recessed part has a peripheral side wall surface with a circular cross sectional outline along planes perpendicularly arranged relative to a fuel injection center axis of the fuel injector. Moreover, the recessed part is tapered along an entire depth of the recessed part such that an internal diameter of the recessed part increases as it approaches the combustion chamber.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved direct fuel injection internal combustion engine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.